1. Field of the Invention
This invention provides a baffle configured to enclose a speaker enclosure that is capable of minimizing propagation of vibrational energy and resonant mode behavior while providing high strength and rigidity.
2. Related Art
Loudspeakers are devices that can convert electrical signals into acoustical energy using transducers. Loudspeakers typically include a front baffle comprising an enclosure. Located within the enclosure is at least one transducer. The outer frame of the transducer may be made of metal or plastic. As the voice coil moves back and forth to create the acoustical sounds, vibrations created from movement of the voice coil often is radiated to the walls of the loudspeaker enclosure by the transducer frame. These vibrations often propagate freely throughout the enclosure exciting panel resonance. The re-radiation of energy is undesirable because it can be perceived as distortion and coloration of the primary signal in the frequency range between 20 Hz to 20 kHz. The re-radiation energy may occur at certain frequencies called re-radiation points or resonant modes. These points or modes may act as undesired phantom sound sources that can compromise the sound field imaging capabilities of the loudspeaker.
Several approaches have been taken to address the problems of panel resonance and re-radiation of energy such as: (1) using a “soft” mounting system to decouple the transducer from the front baffle; (2) adding internal bracing and increasing wall rigidity to increase the frequency of panel resonant modes; (3) adding extensional damping materials and compounds to the interior surfaces of the cabinet walls to damp the internal vibrational energy; and (4) casting the front baffle from energy absorbing materials. All of these approaches, however, have their own limitations.
Using a soft mount system is undesirable because it prevents the transducer from utilizing the overall mass of the loudspeaker cabinet to minimize unwanted motion of the transducer frame. When a soft mounting system is used between the transducer and the loudspeaker cabinet, a loss in perceived fidelity may result from movement of the transducer relative to the enclosure. This loss of perceived fidelity is particularly noticeable in low frequency.
Adding internal bracing and stiffening of the enclosure wall may push the panel resonant modes to higher frequencies where they may cause less audible damage. This, however, may be inadequate because the resonant modes may still exist at higher frequencies. Also, internal bracing and stiffening of the enclosure walls increases the weight of the loudspeaker. This makes it more difficult to handle and transport the loudspeaker.
Adding external damping materials or compounds to the inside of the enclosure is generally only effective in dampening in the high frequency range. The thickness and composition of the damping material may be critical, and at least 50% of the surface area of the interior walls may need to be covered to be effective. Accordingly, adding dampening material adds cost and time to manufacture the loudspeaker.
Casting a baffle from an acoustically “dead” material is problematic because attaching a heavy baffle to the loudspeaker cabinet can compromise the mechanical integrity of the overall loudspeaker. The heavy baffle usually also requires a complicated system of gaskets and screws to enclose the baffle over the cabinet, and because of added weight; it can be more difficult to handle and transport.
Accordingly, there is a need for a baffle that is easy to manufacture and minimizes distortion of the sound being generated by the transducer. Additional needs include providing a baffle that is impact resistant, has sufficient rigidity or stiffness, and optimizes the special separation between the high frequency horn and the woofer.